Golf car having disk brakes and single point latching brake

ABSTRACT

A golf car having a hydraulic fluid brake system. The hydraulic fluid brake system is implemented as a disk brake system which is responsive to hydraulic fluid pressure generated from a master cylinder. A brake pedal and associated linkage provides input to a master cylinder to generate a hydraulic fluid pressure to control a brake caliper assembly. The brake pedal has a range of travel, where a first portion of the range defines a service mode of operation and a second portion of the range defines a parking mode of operation. In the parking mode of operation, the brake pedal and linkage engages a detent to maintain application of the brake to provide a parking mode of operation. An accumulator in the brake system provides an input force to maintain hydraulic fluid pressure sufficient to retain a parking mode of operation.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/517,302, filed Mar. 2, 2000, which claims the benefit ofpriority of U.S. Provisional Application Ser. No. 60/122,405, filed Mar.2, 1999, the entire contents of which are hereby expressly incorporatedby reference into the present application.

BACKGROUND

[0002] 1. Technical Description

[0003] The present invention relates generally to golf cars having diskbrakes and, more particularly, to golf cars having hydraulicallyactuated disk brakes, a single point latching mechanism, and anintegrated accelerator pedal and brake pedal release of the brake systemwhen in a parking mode.

[0004] 2. Description of Related Art

[0005] Most golf cars, and other small utility vehicles, have brakesystems in one form or another. Examples of such systems may be foundwith reference to U.S. Pat. No. 4,867,289, U.S. 5,158,415, and U.S.5,713,189, the disclosures of which are incorporated by reference hereinfor their technical teachings. While the above referenced patentdocuments, and other references, discuss application of brakes toutility vehicles and golf cars, brake systems for small vehicles andgolf cars may yet be improved to increase the ease of use, feel,performance, serviceability, and the like.

[0006] The typical golf car brake system includes a brake pedal andinterconnected accelerator pedal. When the brake pedal is depressed apredetermined distance, the brake system operates in a normal or servicemode. Depressing the brake pedal further engages a parking mode whichmaintains the golf car in a stationary position. When engaging theparking mode, most brake pedals have numerous mechanical detentpositions to enable progressive application of increasing braking force.In some golf cars, the first detent position does not apply sufficientbraking force to maintain the golf car in a stationary position.However, because each detent position often generates an audible click,an operator may assume that the parking brake has been sufficientlyengaged when the parking brake has yet to be sufficiently engaged.Further, conventional brake systems are mechanically sprung to returnthe brake pedal to a non-depressed position. When disengaging theparking brake, such brake systems often generate a particularly loud,audible pop which can be somewhat distracting to the operator.

[0007] It is therefor an object of the present invention to provide abrake system for a golf car which significantly improves upon the priorbrake systems.

[0008] Lightweight off-road utility vehicles used as personnel and cargocarriers, such as golf carts, are much smaller than conventionalautomobiles used on the highways. Their tires and wheels are muchsmaller, and the space beneath the vehicle body is much smaller, thusproviding much less room for the mounting of braking mechanisms at therear wheels. While the brakes used on golf cars have historically beenvery satisfactory for stopping purposes, the service interval betweenchanging of brake pads or shoes has been relatively short, and often isabout one year for a golf car that sees extensive use. As labor costsmount for golf course operators and the like, there is a growingperception that is would be desirable to have a brake system whose padsor shoes last longer than conventional brakes, thus reducing the overallcosts of providing periodic brake service to the vehicles and allowingthe vehicles to be in service for longer periods of time, before beingpulled out of service for a brake inspection and possible brakepad/brake shoe replacement. Further, when pulled out of service, thereis a continuing need to minimize downtime and to minimize the difficultyand amount of labor required to replace the brake shoes or pads.

[0009] Accordingly, another object of the present invention is toprovide an improved braking mechanism that will have a long service lifefor use on the rear wheel of small off-road utility vehicles such asgolf cars that have small wheels and wide tires. A related object is toprovide a disk brake caliper mechanism that is easy to service, and thatrequires minimal disassembly to change the replaceable brake pads withinthe brake caliper assembly. A further object is to provide an extremelycompact construction for a robust hydraulic disk brake assembly which isable to fit within the very confined space in the vicinity of the wheelhub and wheel rim of a small-size off-road vehicle such as a golf car. Arelated object is to provide a compact construction for a brake caliperassembly which features excellent parking braking power and a very longservice life between brake pad changes. Another object is to provide aneasily-assembled yet compact brake caliper assembly that is of very lowprofile, such that it can fit between a small-diameter wheel rim and thecentral cylindrical housing portion of a hub and rotor assembly on aconventional light-weight utility vehicle having a small diameter widewheel rim associated with wide-profile tires such as those found on agolf car.

SUMMARY OF THE INVENTION

[0010] The present invention is directed to a golf car including a framesupported on a plurality of wheels. A prime mover provides driving forceto selected wheels to displace the golf car. The golf car also includesan operator or passenger area supported by the frame and an integratedbrake pedal and accelerator pedal assembly. A hydraulically operatedbrake system receives input from the brake pedal and generates an outputto control a hydraulically operated braking device. The brake systemoperates in a normal mode by partially depressing the brake pedal, andthe brake system operates in a parking mode by depressing the brakepedal further. When the brake system is in the parking mode, the brakesystem may be released by depressing either the brake pedal oraccelerator pedal.

[0011] The present invention is also directed to a brake system for agolf car including an integrated brake pedal and accelerator pedalassembly. A hydraulic brake actuation system receives input from thebrake pedal and generates an output to control a hydraulically operatedbraking device. An accumulator stores braking energy when in a parkingmode and maintains a predetermined minimum hydraulic pressure throughoutthe brake system. The brake system operates in a normal mode bypartially depressing the brake pedal, and the brake system operates in aparking mode by depressing the brake pedal further. When the brakesystem is in the parking mode, the brake system may be released bydepressing one of the brake pedal or accelerator pedals.

[0012] The present invention is also directed to a golf car including aframe supported on a plurality of wheels. A prime mover provides drivingforce to selected ones of the plurality of wheels to displace the golfcar. An integrated brake pedal and accelerator pedal assembly includes abrake pedal having a range of travel. A first portion of the range oftravel defines a service mode of operation, and a second portion of therange of travel defines a parking mode of operation. The integratedbrake pedal and accelerator pedal assembly includes a lock position forthe parking mode of operation and generates a single audible sound whendepressed to the lock position. A hydraulically operated brake systemreceives input from the brake pedal and generates an output to control ahydraulically operated braking device. When the brake system is in theparking mode, the brake system may be released by depressing one of thebrake pedal or accelerator pedal.

[0013] This invention is also directed to a golf car including a framesupported on a plurality of wheels. A prime mover provides driving forceto selected ones of the plurality of wheels to displace the golf car. Anintegrated brake pedal and accelerator pedal assembly. A hydraulicallyoperated brake system receives input from the brake pedal and generatesa hydraulic output signal. A brake rotor attaches to at least one of thewheels of the golf car. A first caliper assembly has brake padsdisplaceable in accordance with the hydraulic output signal. The brakepads contact the brake rotor to cause friction. The friction retardsmovement of the brake rotor and associated wheel. The brake systemoperates in a normal mode by partially depressing the brake pedal. Thebrake system operates in a parking mode by depressing the brake pedalfurther. When the brake system operates in the parking mode, the brakesystem may be released by depressing one of the brake pedal oraccelerator pedals.

[0014] For a more complete understanding of the invention, its objectsand advantages, reference should be made to the following specificationand to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings, which form an integral part of the specification,are to be read in conjunction therewith, and like reference numerals areemployed to designate identical components in the various views:

[0016]FIG. 1 is an elevational, partial cut-away view of a golf carincluding a brake system arranged in accordance with the principles ofthe present invention;

[0017]FIG. 2 is a block diagram of the brake system arranged inaccordance with the principles the present invention;

[0018]FIG. 3 is a perspective view of the golf car support frame andcomponents of the brake system;

[0019]FIG. 4 is an assembled view of the brake and accelerator pedalassembly;

[0020]FIG. 5 is an exploded view of the brake pedal and the acceleratorpedal assembly;

[0021]FIG. 6 is a top view of the brake pedal and accelerator pedalassembly;

[0022]FIGS. 7 and 8 are a partial, vertical sectional views of the brakepedal and accelerator pedal assembly;

[0023]FIG. 9 is a graph depicting hydraulic pressure as a function ofbrake pedal displacement;

[0024]FIG. 10 is a block diagram of a brake system of the presentinvention utilizing a drum brake system;

[0025]FIG. 11 is a block diagram of the brake system of the presentinvention utilizing a brake band system;

[0026]FIG. 12 is an interior perspective view of a hub and caliperassembly;

[0027]FIG. 13 is an exterior perspective view of a hub and caliperassembly;

[0028]FIG. 14 is an exploded view of a caliper assembly of FIGS. 12 and12;

[0029]FIG. 15 is an expanded perspective view of the caliper assembly;

[0030]FIG. 16 is a bottom view of the caliper assembly; and

[0031]FIG. 17 as an elevational view of the integral wheel, hub, androtor assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032]FIG. 1 depicts a golf car 10 having a brake system arranged inaccordance with the principles of the present invention. Golf car 10includes a pair of front wheels 12 and a pair of rear wheels 14. Rearwheels 12 preferably operate as steering wheels to control the directionof travel of golf car 10. Rear wheels 14 preferably function as drivewheels for propelling golf car 10.

[0033] Golf car 10 includes a seat 16 which preferably accommodates adriver and a passenger. Golf car 10 also includes a steering wheel 18which controls the direction of front wheels 12. An accelerator pedal 82and a brake pedal 80 enable the operator to control acceleration andbraking of golf car 10. Accelerator pedal 82 and brake pedal 80preferably are suspended from support members which hang generallydownwardly from underneath a front cowling 24, as will be describedherein.

[0034] Still referring to FIG. 1, an entire brake actuator and releaseassembly 50 is configured as a modular unit mounted above the floorboard26 and at least partially beneath the front cowling 24. It thereforelacks any underhanging components that extend beneath the floorboard 26.This configuration is advantageous for several reasons. For instance,there is no risk that any components of the brake system 50 will bedamaged by obstructions over which golf car 10 may travel. Moreover, thesystem components are isolated from corrosive substances over which thevehicle may travel such as water, fertilizers, etc.

[0035]FIG. 2 depicts a particular feature of golf car 10, namely, brakesystem 50. Accelerator pedal 82 controls operation of an electric motor32 which is powered by a source of electrical energy (not shown).Electric motor 32 includes one or a pair of output shafts 34 whichcontrol drive to respective hubs 38. It should be noted that referencenumerals in the drawings may include an R or L suffix to designate acomponent as corresponding to the left or driver's side or the right orpassenger's side of golf car 10. Respective hubs 38 drive rear wheels 14to propel golf car 10. While motor 32 is described herein as an electricmotor, one skilled in the art will recognize that rear wheels 14 may bepropelled by a gasoline powered engine and transmission or othersuitable power source.

[0036] Brake system 50 will generally be described herein as ahydraulically actuated brake system wherein displacement of brake pedal80 generates a hydraulic force to operate a braking element, such as adisk, drum, or band brake system, as will be described herein. Brakesystem 50 includes brake pedal 80 which connects to and displaces alinkage 42. Linkage 42 provides an input to a master cylinder 60. Mastercylinder 60 operates generally as a conventional master cylinder inwhich depressing brake pedal 80 provides an input to master cylinder 60which generates an increase in hydraulic fluid pressure output onhydraulic control line 46.

[0037] Hydraulic control line 46 provides fluid pressure to caliperassemblies 48. Each caliper assembly 48 includes opposing pads 44. Abrake rotor 40 moves rotationally in accordance with hubs 38. Pads 44apply a frictional force to brake rotor 40 to retard movement of brakedisk 52, thereby applying a braking force upon wheels 14. Caliperassemblies 48 thus operate generally as is known to one skilled in theart. In order to maximize braking force, an optional second pair ofcaliper assemblies 54 may be arranged to provide additional retardingforce upon brake rotor 40. A particularly attractive feature ofutilizing two caliper assemblies on a single brake disk is to compensatefor space limitations inherent with the generally small diameter ofwheels 14 of a typical golf car 10.

[0038] As described above, depressing brake pedal 80 causes mastercylinder 60 to generate a hydraulic fluid output pressure on hydrauliccontrol line 46 which is applied to caliper assemblies 48 and tocalipers assemblies 54 if present. An increase in hydraulic fluidpressure causes brake pads 44 to move toward brake rotor 40 to generatea frictional force which retards movement of wheels 14.

[0039] Brake system 50 has two modes of operation. A first mode ofoperation, a service mode, of brake system 50 reduces the speed of golfcar 10 to a lower speed, a stop, or to prevent unwanted acceleration ofgolf car 10 when going down hill. A second mode of operation, a parkingmode, of brake system 50 maintains golf car 10 in a stopped positionuntil the parking mode has been released.

[0040] Brake pedal 80 has a range of travel for causing master cylinder60 to output a hydraulic fluid pressure suitable for stopping golf car10 or maintaining golf car 10 in a stopped position. A first portion ofthe range of travel of pedal 80 effects a service mode of operation forreducing the speed of golf car 10 or to prevent unwanted acceleration ofgolf car 10 when going down hill. Depressing brake pedal 80 furtherplaces brake system 50 in a parking mode. Linkage 42 includes a detentsetting for engaging and holding brake pedal 80 in a predeterminedposition while in the parking mode. When in this parking mode, theaccumulator 62 provides a supplemental input to master cylinder 60 tocompensate for any hydraulic fluid pressure drop through seal leakageand the like. Accumulator 62 maintains hydraulic fluid pressure so thatcaliper assemblies 48 provide suitable parking brake force upon brakerotor 40 and associated wheels 14.

[0041] Brake pedal 80 and linkage 42 cooperate to include a singledetent which is engaged when brake pedal 80 travels a predetermineddistance so as to cause master cylinder 60 to output a sufficienthydraulic fluid pressure to prevent displacement of wheels 14. Whenbrake pedal 80 has engaged a detent position to define a parking mode ofoperation, brake system 50 can be disengaged from the parking mode ofoperation by depressing either brake pedal 80 or accelerator pedal 82.Accelerator pedal 82 is mechanically linked to brake pedal 80 to enablerelease of the brake system 50 from the parking mode of operation.

[0042] With particular reference to FIG. 3, golf car 10 includes avehicle frame 56. Frame 56 provides a support to which brake andaccelerator pedal assembly 58 connects. Rear axle assembly 64 supports arear portion of frame 56 via a suspension (not shown). As shown in FIG.3, brake and accelerator pedal assembly 58 mounts to an upper portion 52of frame 56 so that brake pedal 80 is suspended downwardly on lever arm88 and accelerator pedal 82 is suspended downwardly upon accelerator arm172.

[0043] Several features of brake system 50 will now be described. Whenthe parking mode is engaged, brake system 30 generates a single audibleclick or pop sound. The sound indicates that the parking mode has beenproperly engaged by the operator. The benefit of a single audible soundis to provide a clear indication that the parking mode has been engaged.This feature improves upon conventional braking systems where multipleaudible sounds may be generated when engaging a parking mode. In suchsystems the operator could incorrectly assume that while the brake pedalis locked in a position that generates a sufficient braking force, aninsufficient parking brake force could be applied.

[0044] Brake system 50 inherently has less hysteresis associated withstiction than brake systems utilizing mechanical components,particularly hysteresis caused by cables running over contact points.Reduced hysteresis provides a brake system 50 which requires less forcefor selecting either the service or parking modes verses a mechanicalsystem which requires greater force to properly engage a service orparking mode. Because hysteresis is inherently less in a hydraulicsystem and because hysteresis in mechanical systems typically increasesover time, hydraulic brake system 50 significantly reduces hysteresisconcerns problem over the lifetime of golf car 10.

[0045] Hydraulic brake system 50 has a self-adjusting system whichcompensates for wear in brake pads 44. Self adjustment occurs becausethe system allows extra fluid from the hydraulic reservoir of mastercylinder 60 to be added to the system. Using caliper design featureswell known in the art, the seals of the hydraulic cylinders in the brakecalipers insure a uniform return of brake pads 44 to equal distancesaway from brake disk 52. These benefits may be further realized byutilizing a bladder-based hydraulic reservoir which provides severaladditional advantages. The bladder type hydraulic reservoir ensuresminimal loss of hydraulic fluid through the top of the reservoir. Thisavoids introduction of contaminants such as water, dirt, and atmospherictransfer which may occur.

[0046] Hydraulic brake system 50 utilizes a synthetic fluid which isnon-hygroscopic. A non-hygroscopic fluid does not absorb any fluid.Conventional brake fluid, on the other hand, absorbs moisture directlythrough rubber hoses and seals and other places where conventional brakesystems are open to the atmosphere, including the reservoir. Thistransfer occurs even through seals which are frequently water vaporpermeable. Thus, while many seals resist moisture in a liquid form, manysuch seals do not resist moisture in the form of a gaseous vapor.Hygorscopic brake fluid also often accelerates internal breakdown ofmetal brake system parts, while non-hygroscopic, synthetic fluidsignificantly reduces internal breakdown of metal brake system parts.Non-hygroscopic fluids provide a non-polar property, which yields anenvironmentally friendly brake fluid. Most grass plants will not absorbthe non-hygroscopic, synthetic fluid, while typical conventional brakefluids may be absorbed by and damage plant life yet.

[0047] Conventional brake fluids, while possibly avoiding waterabsorption, also absorb air. The absorption of air into the brake fluidcreates a spongy brake feeling and can also raise other issues such ascavitation and outgassing. Outgassing occurs when a vehicle remainsexposed for a lengthy period of time in a high altitude condition.Bringing the golf car down to lower elevations and thus higheratmospheric pressure causes air entrained in the liquid at higherelevations to boil off at the lower elevations. This introducesvariation into the hydraulic system.

[0048] Hydraulic brake system 10 also provides a positively-sealed,pressurized hydraulic brake system. In a parking mode, hydraulic brakesystem 10 generates at least 750 pounds per square inch (PSI). Thispressurization exceeds internal hydraulic fluid pressure typicallyutilized in conventional hydraulic braking systems, particularly atrest. In conventional hydraulic braking systems, the parking mode isengaged through a mechanical-type emergency brake or transmission lock.Brake system 50 utilizes a hydraulic system which is continuouslypressurized when the golf car is not in use and the brake system isengaged in a parking mode. To achieve a positive seal in response torelatively high static hydraulic pressures present in brake system 50,eleastometer seals replace metal-to-metal contact on all sealingsurfaces, including air bleeder valves found on caliper assemblies 48.

[0049] Hydraulic brake system 50 also includes two separate dampingsystems to provide a controlled release of brake pedal 82. A firstdamping system is a mechanical damping system implemented by applying adamping grease to a pivot shaft housed within a stationary sleeve. Thehelical spring returns brake pedal 82 to its non-operative position. Thedamping grease has a viscosity which varies in accordance with thedisplacement speed of the pivot shaft. At slower speeds, the dampinggrease acts as a lubricant. At higher speeds, the damping greaseprovides a viscous action between two adjacent surfaces which retardsthe rate at which the pivot shaft may be rotated with respect to thestationery sleeve. Thus, the damping grease is applied to both the pivotshaft and the stationary sleeve. As the pivot shaft rotates with respectto the stationary sleeve, the viscous action ensures a controlled rateof upward travel of brake pedal 82. This viscous action alsosignificantly reduces the normal multiple vibration pulses that occur atthe top of the brake pedal stroke in convention mechanical systems.

[0050] A second damping system utilizes a dampened hydraulic fluid flowto maintain a controlled return of parking brake 82 pedal to itsnon-operative position. This controlled rate of upward movementminimized noise inherent in the stopping of brake pedals at the top oftravel in conventional brake systems.

[0051] Hydraulic fluid travels through a spiral grooved return path torestrict hydraulic fluid flow during pedal return. The fluid dampingpath enables a fluid flow return rate which encourages the brake pedalupward at a reasonable rate so as to maintain contact with the foot ofthe operator while the operator lifts upward with his or her foot. Thus,the operator feels the brake pedal firmly on the bottom of theoperator's foot, while the return rate is sufficiently slow to preventbanging when the brake pedal reaches the top of travel.

[0052] Referring now to FIGS. 4-8, a preferred mode of practicing theinvention will be described. The brake actuator and release assembly 50includes as its major components 1) a master cylinder 60, 2) a hydraulicaccumulator 62, and 3) an integrated brake pedal and accelerator pedalassembly 58. All of these components are mounted on a common supportbracket 66 that is formed from a single metal stamping. As best seen inFIGS. 4-8, the support bracket 66 has an open rear end, inboard andoutboard sidewalls 68 and 70, and a front wall 72 connecting thesidewalls 68 and 70 to one another. Mounting flanges 74, 76, and 78extend outwardly from the sidewalls 68 and 70 and the front wall 72 forconnection to a support such as the front wall 42 of the operator'scompartment.

[0053] The integrated brake pedal and accelerator pedal assembly 58 andthe hydraulic accumulator 62 can be used either in combination orindependently of one another and are applicable to the illustrated brakesystem 50 as well as to a variety of other systems. Each of thesecomponents will be described in turn.

[0054] The integrated brake pedal and accelerator pedal assembly 58 isusable with the hydraulic brake system 50 as well as a more traditionalmechanical cable-actuated brake system. It includes a brake pedal 80, anaccelerator pedal 82, and a locking mechanism 84. The assembly 58 canperform several distinct functions. First, the brake pedal 80 can beactuated to perform a service braking operation. Second, the lockingmechanism 84 can latch the brake pedal 80 in a locked, actuated positionto hold the service brakes 52 in their engaged position. Third, thebrake pedal 80 can operate, in conjunction with the accumulator 62, tofacilitate brake pedal latching and store energy to help assure that thebrakes 52 will remain in their locked position despite creep that mayoccur within the system. Fourth, the locking mechanism 84 can bereleased using either the brake pedal 80 or the accelerator pedal 82without actuating any secondary brake release mechanism.

[0055] The brake pedal 80 includes a pivot shaft 86, a lever arm 88extending downwardly from the pivot shaft 86, and a pad 90 mounted onthe bottom end of the lever arm 88. As best seen in FIGS. 6, 7, and 8,the pivot shaft 86 is mounted on a plastic sleeve 92 so as to berotatable with respect thereto, and the plastic sleeve 92 is, in turn,mounted on a main pivot shaft 94. Shaft 94 is rotatably supported on thesupport bracket 66 and also serves as the pivot shaft for theaccelerator pedal 82 (discussed below). The pivot shaft 86 is lubricatedvia a synthetic damping grease injected into the space between the pivotshaft 86 and the plastic sleeve 92. The damping grease preferably thatcomprise one that exhibits good lubrication characteristics at lowrotational velocities but that actually serves to damp or inhibit shaftrotation at higher rotational velocities. The preferred grease is NYEPG-44A, which is manufactured by NYE Lubricants, Inc. This grease is anextremely stiff consistency, inorganically gelled, water resistant,rust-inhibited damping grease based on a high molecular weightpolymeric-base oil. The lever arm 88 preferably is formed from steelencased in a plastic sleeve (not shown) in order to protect the steelfrom corrosion. The pad 90 may comprise any suitable foot actuated padmounted on the end of the lever arm 88. A torsion spring 96, serving asa brake pedal return spring, is mounted on the pivot shaft 86 on oneside of the lever arm 88. In addition, a plastic block 98 is mounted onthe upper surface of the lever arm 88 to form part of the lock mechanism84 as detailed below.

[0056] Referring particularly to FIG. 5, a master cylinder actuating pinsupport arm 100 is mounted on the pivot shaft 86 adjacent the inboardside of the lever arm 88 so as to rotate with the lever arm 88. Anactuating pin 102 is mounted on the support arm 100 so as to rotate withthe pivot shaft 86. The pin 102 is coupled to a main piston 104 of themaster cylinder 60 via a roller 103 and a strap 105 so that the brakepedal 80 and master cylinder piston 104 always move together. Theactuating pin 102 comprises an eccentric pin that is mounted in anaperture 106 in the support arm 100 so as to extend laterally toward thebrake lever arm 88. A head 108 on the pin 102 can be rotated to rotatethe thicker portion of the eccentric pin 102 either towards or away fromthe master cylinder main piston 104, thereby eliminating any play ordead space between the brake pedal 80 and the master cylinder mainpiston 104 after assembly of all components.

[0057] The locking mechanism 84 is operable to automatically latch thebrake pedal 80 in its locked position upon depression of the brake pedal80 to a latch point and to automatically unlatch the brake pedal 80 fromits locked position to release the brakes 52 upon brake pedal overtravelbeyond the latch point. The locking mechanism 84 also is configured torelease the brake pedal 80 under power of the accelerator pedal 82. Thelocking mechanism 84 may comprise any structure having at least oneof 1) single point latching capability, 2) the ability to release thebrakes 52 upon brake pedal overtravel beyond its latched position, and3) a kickoff mechanism that permits accelerator pedal release of thebrake pedal 80. The illustrated locking mechanism 84 includes the block98 on the brake pedal lever arm 88, a control arm 110 pivotally mountedon the brake pedal 80, a swing arm 112 pivotally mounted on the supportbracket 66, and an over-center spring 114 that is coupled to the controlarm 110 and to the swing arm 112 so as to bias the swing arm 112downwardly during service braking and to bias the swing arm 112 upwardlyduring a latch and release cycle.

[0058] The control arm 110 comprises a metal plate pivotally mounted onthe block 98 of the brake pedal 80 via a pivot pin. Control arm 110 hasinner and outer faces and front and rear ends. The rear end presentsdetents 118 and 120, and a lug 122 is mounted on the outer face near therear end near the axis of the pivot pin. During a brake lock and releasecycle, detents 118 and 120 cooperate with a dog or pawl 124 on the swingarm 112. A cushioned stop is mounted on the inner face of the controlarm 110 in front of the pivot pin. The stop has first and second arcuatesurfaces that selectively engage corresponding first and secondcushioned posts on the block 90 during the brake pedal lock and releasecycle as detailed below. Finally, a post 136 extends outwardly from afront end portion of the outer face of the control arm 110 forconnection to a front end of the over-center spring 114.

[0059] The swing arm 112 supports the dog 124 and the cam 125. It alsosupports a cam follower 138 that rides along a cam 140 on the block 98.The entire swing arm 112 is mounted on a pivot tube 142 that extendslaterally across the support bracket 66 and that is rotatably supportedon a support pin 146. Support pin 146 is, in turn, mounted in aperturesin the opposed sidewalls 68 and 70 of the support bracket 66. A pair ofcam follower support arms 144 extend forwardly from the pivot tube 142in a spaced-apart relationship. The cam follower 138 is rotatablymounted on the front ends of the support arms 144, and a cushionedelastomeric bumper 148 is mounted on the rear ends of the support arms144. The cam follower 138 comprises a roller mounted on the support arms144 by a roll pin. The bumper 148 serves as a stop for the brake pedal80 when the brake pedal is in its at rest or fully released positionseen in FIG. 7. The dog 124 is positioned laterally outwardly of theoutboard cam follower support arm 144 and is configured to cooperatewith the detents 118 and 120 on the control arm 110. The cam 125 isformed from a common stepped lug with the dog 124 and is positioned soas to be engaged by the lug 122 on the control arm 110 during a latchingoperation. A spring support bracket 150, disposed outboard of the dog124, supports a post 152 to which the over-center spring 114 isconnected. The locations of the posts 152 and 136 on the swing arm 112and the control arm 110 are selected relative to 1) one another, 2) therotational axis of the cam follower, 3) the pivot axis of the brakepedal 80, and 4) the pivot axis of the swing arm 112 to cause the spring114 to move across the pivot axis of the swing arm 112 at selectedphases of the brake pedal depression and return processes so as toselectively assist brake pedal locking and unlocking. In the illustratedembodiment, the over-center spring is 30°-40° below the horizontal whenit is in its first over-center position and a corresponding amount abovethe horizontal when it is in the second over-center position.

[0060] The block 98 is mounted directly on the upper surface of thebrake pedal lever arm 88 and serves as a support structure for severalother components of the locking mechanism 84. It has the cam 140 formeddirectly on the upper or rear surface thereof. The cam 140 is straightalong the majority of its length but has an arcuate portion 154 at itslower end surface formed from a cutout in the block 98. Arcuate portionis dimensioned such that the cam follower 138 will rest in the arcuateportion 154 in a locked position of the brake pedal 80.

[0061] A generally L-shaped toggle arm 156 is pivotally mounted on theinner lateral surface of the block 98 adjacent the swing arm 112. Thetoggle arm 156 includes 1) a first leg 158 and 2) a second leg 160 thatextends generally orthogonally from the first leg 158. The first leg 158is biased into contact with a post 162 on the block 98 by a returnspring 164. The second leg 160 cooperates selectively with a lug 166 onthe swing arm 112 so as to prevent swing arm pivoting motion during theinitial phase of brake pedal depression and to subsequently permit theswing arm 112 to fall into its locking position when the lug 166 clearsthe second leg 160, thus allowing only one contact sound to be heard.

[0062] Finally, a kickoff arm 170 is mounted on the inboard end of thepivot tube 142 at a location beyond the inboard cam follower support arm144. The kickoff arm 170 extends forwardly and outwardly from the pivottube 142 so as to extend beyond the inboard sidewall 70 of the supportbracket 66 and so as to be engaged by the accelerator pedal 82 uponinitial accelerator pedal depression.

[0063] The accelerator pedal 82 is mounted on the inner distal end ofthe pivot shaft 94 at a location outside of the inboard sidewall 70 ofthe support bracket 66. It includes 1) a lever arm 172 that extendsdownwardly from the pivot shaft 94 and 2) a pad 174 that is mounted onthe distal end of the lever arm 172. A portion of the lever arm 172 ispositioned closely adjacent the kickoff arm 170 so as to engage thekickoff arm 170 upon initial accelerator pedal depression. In addition,a non-contact accelerator pedal position sensor 178 is positioned insidethe lever arm 172 in order to provide an indication of accelerator pedalactuation. The accelerator pedal 82 is biased to its deactuated positionby a return spring 180.

[0064] In operation, the integrated brake pedal and accelerator pedalassembly 54 assumes the position illustrated in FIGS. 5-6 when thebrakes 52 are not engaged. At this time, the brake pedal 80 assumes anat rest or fully released position in which it is pivoted to itsrearward-most extent in which the front face on the block 98 engages thebumper 148 on the swing arm 112. The cam roller 138 on the swing arm 112is located at its maximum possible distance from the arcuate portion 154of the cam 140. In addition, the over-center spring 114 is in its firstover-center position in which it biases the control arm 110 to theposition in which its centerline is beneath the pivot axis of the swingarm 112. It therefore biases the swing arm 112 downwardly.

[0065] Next, the operator engages the brakes 52 by pressing downwardlyon the pad 90 to swing the brake pedal 80 clockwise into a servicebraking position. This pivoting motion causes the master cylinderactuating pin 102 to drive the roller 103 and master cylinder mainpiston 104 forwardly to effect service braking. After the servicebraking stroke ends, but before the brake pedal 80 reaches it latchpoint, the lug 166 on the swing arm 112 rides along the second leg 160of the toggle arm 156 to hold the cam roller 138 away from the cam face140 and to hold the dog 124 and cam 125 on the swing arm 112 away fromthe control arm. As a result, service braking and subsequent brake pedaldepression toward the latch point occur without contact between thelatching components of the locking mechanism 84, thereby avoiding thegeneration of contact sounds that otherwise could give a false audibleindication of pedal locking. The over-center spring 114 remains in itsfirst over-center position at this time. The control arm 110 thereforeremains in the position in which it cannot latch against the swing arm112. As a result, the brake pedal 80 will return to its releasedposition if the operator removes his foot from the pad 90 withoutadditional brake pedal depression.

[0066] At the end of service braking stroke and well beyond it, the lug166 on the swing arm 112 clears the second leg 160 of the toggle arm 156so that the swing arm 112 drops through an arc to a position in whichthe cam 125 engages the lug 122 on the control arm 110. This delayeddropping of the swing arm 112 has several benefits. For instance, asdescribed above, it permits the dog 124 and cam 125 on the swing arm 112to clear the detents 118 and 120 and the dog 122 on the control arm 110so as to prevent a false audible indication of brake pedal locking.Moreover, it prevents the swing arm 112 from swinging towards its lockedposition until the over-center spring 114 is stretched sufficiently tostore enough potential energy to effectively assist in swing armmovement into its locked position. In addition, the solid contactbetween the cam 125 and the lug 122 that occurs when the swing arm 112drops into place produces a distinctive “clicking” sound that providesan audible indication to the operator that the brake pedal 80 has movedinto a position in which it can be locked.

[0067] When the operator releases his foot from the brake pedal 80 afterdepressing it to its locked position, the brake pedal returns a verysmall amount to permit the over-center spring 114 to move from its firstover-center position to the second over-center position as a result ofthe swing arm cam 125 pushing the control arm dog 122. As a result ofthis movement, the control arm 110 pivots rapidly from this position tothe latched position. Because the dog 122 is located very close to thepivot axis of the control arm 110, a very small range of axial brakepedal movement (on the order of a few thousands of an inch) results in60° or more of control arm pivoting movement. This relationship reducesthe work required of the over-center spring 114 during the latchingprocess. The second face 130 on the stop 126 now engages the second post134 on the block 98, and the first or lower detent 118 on the controlarm 110 now engages the dog 124 on the swing arm 112 to lock the swingarm 112 in position. This motion provides a distinctive clicking soundthat provides an audible indication to the operator that the brake pedal80 has been locked. The brake pedal 80 will thereafter remain in thelocked position under the latching force of the control arm 110 when theoperator releases the brake pedal 80. However, because the spring 114 isnow in is second over-center position in which its centerline is abovethe pivot axis of the control arm 112, it biases the control arm 112upwardly rather than downwardly, thereby priming the control arm 112 forsubsequent release.

[0068] The holding force applied on the control arm 110 by theover-center spring 114 at this time should be large enough so as not tobe overcome by any force that might inadvertently be placed upon orgenerated through the accelerator pedal 82 by virtue of the vehicle 30being jostled during shipment or by rough treatment by errant operators.However, this holding force need not be very large because any momentarm which might tend to cause the swing arm 112 to swing out of itslocked position is very small. As a result, a relatively weak spring(having a spring load on the order of 8-12 lb can be used as theover-center spring 114.

[0069] The brakes 52 may be released by operating either the brake pedal80 or the accelerator pedal 82 to unlatch the brake pedal 80 from itslocked position. To release the brakes using the brake pedal 80, all theoperator need do is depress the pedal 80 beyond its locked position toan overtravel position. This brake pedal movement and consequent swingarm movement will cause the dog 124 on the swing arm 112 to slip out ofthe first detent 118 on the control arm 110, permitting the over-centerspring 114 to pull the swing arm 112 upwardly so that dog 124 snapsagainst the second detent 120 as seen in FIG. 10. The snapping action ofthe dog 124 against the detent 120 produces a distinctive click thatapprises the operator that the brake pedal 80 is unlatched. As a result,the brake pedal 80 will return to its at-rest position under the biasingforces of the return spring 96 and the accumulator spring 246 when theoperator releases the brake pedal 80.

[0070] The brake pedal 80 places a substantial moment on the swing arm112 during the return stroke of the brake pedal 80. The dog 124 on theswing arm 112 produces a corresponding moment on the upper surface ofthe detent 120 of sufficient magnitude to pivot the control arm 110counter-clockwise. The over-center spring 114 therefore moves back toits first over-center position so that it again biases the swing arm 112downwardly. In addition, the lug 166 on the inner lateral surface of theswing arm 112 engages the second leg 160 of the toggle arm 156 duringthe return stroke to cause the toggle arm 156 to pivot clockwise topermit unobstructed movement of the lug 166 past the toggle arm 156. Thetoggle arm 156 then drops back into its initial position under thebiasing force of the spring 164 so that it is primed for the nextservice braking cycle.

[0071] Brake pedal release using the accelerator pedal 82 occurs insimilar sequence. The operator presses downwardly on the acceleratorpedal 82 so that the lever arm 172 engages the kickoff arm 170. Thisengagement forces the swing arm 112 to swing clockwise about the pivottube 142 to drive the control arm 110 to pivot as described above. Asbefore, this movement unlatches the swing arm 112 from the control arm110 and permits the brake pedal 80 to return to its at-rest positionunder the biasing force of the brake pedal return spring 96 and theaccumulator spring 246. Also as before, this movement forces the controlarm 110 and over-center spring 114 back to the initial position. Becausethe cutout 154 in the cam surface 140 is tangential to the swing armpivot arc, the cam roller 138 simply moves circumferentially along thecam surface 140 during the initial, accelerator pedal imposed phase ofthe unlatching operation without resistance from the rather substantialreturn force imposed on the brake pedal 80 by the brake pedal returnspring 96 and the accumulator spring 246. Brake pedal unlatchingtherefore imparts little resistance to accelerator pedal motion, andbrakes 52 are disengaged after the first 1-3 inches of accelerator pedalstroke with minimal operator effort. As a result, the operator can“feather” accelerator pedal motion so that the brakes 52 can bedisengaged without over-depressing the accelerator pedal 82. Thiseliminates jerky motion or quick starts often associated with golf cartsand other light-duty vehicles.

[0072] The master cylinder 60 and hydraulic accumulator 62 areconfigured to translate the mechanical actuating forces generated bybrake pedal depression into hydraulic pressure that first engages thebrakes 52 and that then stores additional energy for holding the brakes52 in their engaged condition. This energy storage provides severalbenefits. For instance, it permits the brake system 50 to make up for“creep” or fluid pressure loss that may occur due, e.g., relaxation ofelastomeric components of the system. Moreover, it can assist inreturning the brake pedal 80 to its at rest position following releaseof a locked brake pedal.

[0073] Referring to FIGS. 4, 5, 7, and 8, the master cylinder 60 isgenerally conventional. It includes a housing 200 having an internalhorizontal bore 202 formed therein. A reservoir 204 is formed above thebore 202 for storing hydraulic fluid. The bore 202 has an upper fillinlet 206 and a rear outlet 208. The inlet 206 cooperates with thereservoir 204. The rear outlet 208 opens into an accumulator chamber210, detailed below. The master cylinder main piston 104 is slidablymounted in the bore 202 so as to extend rearwardly from the rear end ofthe bore 202 and into contact with the roller 103. As a result of thisarrangement, 1) depression of the brake 80 and consequent swingingmovement of the actuator pin 102 and roller 103 drives the main piston104 forwardly through the bore 206 to pressurize the outlet 208, and 2)release of the brake pedal 80 permits the main piston 104 to moverearwardly through the bore 202 to depressurize the outlet 208.

[0074] Referring to FIG. 7, accumulator chamber 210, as well as theremainder of the accumulator 62, may be located at any pressurized pointin the braking system 50. In the illustrated embodiment, however, thechamber 210 is formed in an extension 212 of the master cylinder housing200 extending essentially colinearly with the bore 202 so as to reducethe number of parts in the accumulator 62 and to facilitate assembly.The accumulator chamber 210 has a first orifice 218 in a rear wallthereof that opens directly into the master cylinder outlet 208, and asecond orifice 220 in an upper wall thereof that communicates with ableeder port 222 and a brake supply orifice 224 in the master cylinderhousing extension 212. The orifice 224 is connected to the front and/orrear vehicle brakes 52 via associated brake lines 46 of FIG. 2.

[0075] An accumulator drive piston 214 and a one-way restrictor valve216 are mounted in the accumulator chamber 210. The accumulator drivepiston 214 is slidably mounted in the chamber 210 so as to extend beyonda rear end of the master cylinder extension 212 and into contact withthe accumulator spring assembly 58. The one-way restrictor valve ispositioned forwardly of the accumulator drive piston 214 and is biasedtoward the front of the chamber 210 by a return spring that is seated onthe one-way restrictor valve 216 at its front end and on the accumulatordrive piston 214 at its rear end.

[0076] The purpose of the one-way restrictor valve 216 is to damp returnfluid flow into the master cylinder 60 from the accumulator chamber 210upon release of the brakes 52, thereby inhibiting the pronounced brakepedal snapback effect exhibited by most park and hold brake systems ofthis type. The energy stored in the accumulator 62 and the brakes 52instead is released more gradually, permitting a much smoother brakepedal return.

[0077] The hydraulic accumulator 62 performs several beneficialfunctions. For instance, it reduces the effort required by the operatorto depress the brake pedal 80 to its locked position. It also storesenergy generated upon manual pressurization of the hydraulic fluid in aform that can then be used to maintain the brakes 32 in their engagedpositions after the brake pedal 80 is locked. Finally, it assists inreturning the brake pedal 80 to its released position upon brake pedalunlocking. The preferred accumulator structure is one that has a minimumnumber of components and that can be readily assembled as a unit offsiteand then attached to the remainder of the brake assembly 50 by anunskilled operator. Towards these ends, the hydraulic accumulator 62 isa spring type accumulator taking the form best seen in FIG. 7. Itincludes a retainer 240, a movable compression plate 242 disposed at therear end of the retainer 240, a cap 244 affixed to the front end of theretainer 240, and a compression spring 246 captured between thecompression plate 242 and the cap 244.

[0078] The retainer 240 includes a front mounting plate 248 and aplurality (preferably two) straps 250 that extend rearwardly from themounting plate 248. The mounting plate 248 has an internally threadedpost 252 and a pair of tangs 254 located radially outside of the post254 and bent in opposite directions. The threaded center post 252 screwsonto external threads 256 on the master cylinder housing extension 212,and the tangs 254 lock into slots 258 in the front wall 72 of thesupport bracket 66 when the post 252 is fully tightened onto the mastercylinder housing extension 212. The accumulator 62 can subsequently beunscrewed from the master cylinder housing extension 212 only byovertorquing the accumulator 62 in a counter-clockwise direction torelease the tangs 254 from the slots 258. The straps 250 serve as mountsfor the cap 244 and are configured to guide and support both the spring246 and the compression plate 242. Each strap 250 extends rearwardlyfrom the mounting plate 248 and terminates in a hook 260 at its distalend. The bodies of the straps 250 serve as supports and guides for thecompression plate 242 and the spring 246. The hooks 260 latch onto thecap 244 as detailed below to fix the cap in place.

[0079] The compression plate 242 includes a rear annular spring supportportion 262 and a cup portion 264. The cup portion 264 extends axiallyforwardly from the center of the rear spring support portion 262 to afront nut portion 266. Spring support portion 262 presents a seat forthe rear end of the accumulator spring 246. Cup portion 264 isconfigured to surround the end of the master cylinder housing extension212 and to abut the front end of the accumulator drive piston 214.Apertures 268 are formed in the spring support portion 262 for passageof the straps 250. Upon assembly, this relationship between the straps250 of the retainer 240 and the apertures 268 in the compression plate242 permits the compression plate 242 to move axially relative to theretainer 240 but prevents relative rotational movement between thecompression plate 242 and the retainer 240.

[0080] The cap 244 comprises a metal annular ring having a circularaxially front end portion 270 and inner and outer circular flanges 272and 274. The flanges 272 and 274 extend rearwardly from the front endportion 270 so as to form a groove serving as a second seat for thespring 246. A pair of hook receiving apertures are formed in the frontend portion 270 adjacent to corresponding notches 278. The notches 278are configured to receive the straps 250 and the hooks 260 of theretainer 240, thereby locking the cap 244 onto the retainer 240.

[0081] The spring 246 is precompressed a substantial amount as a resultof a preassembly process. As discussed in more detail below, this springprecompression sets a threshold pressure below which substantially allwork performed by the master cylinder 60 is applied toward fluidpressurization and above which the majority of the work performed by themaster cylinder 60 is applied toward energy storage in the accumulator62. The amount of precompression required for a particularpressurization threshold level will vary depending on the spring rate ofthe spring 246 and its caged height. The spring 246 of the illustratedembodiment has a free length of about 9″ and a spring rate of 25 lbs/in.It is precompressed to an installed length of approximately 4″ duringthe assembly process to provide a threshold pressure of about 800-850psi.

[0082] The precompression of the accumulator spring 246 is selected toset the threshold pressure to a level well above the lockup point of thebrakes 52 but well below the single latch point of the brake pedal 80.In a system in which the brake pedal is latched in position 8″ into itsstroke, service braking is performed in the first 2 to 3″ of brake pedalstroke even under panic stop conditions. In fact, brake lockup typicallyoccurs after no more than 2½″ of brake pedal stroke. Typical lockuppoints for fully burnished and unburnished brakes are denoted as such inFIG. 8.

[0083] Additional brake pedal depression past the threshold point 286compresses the accumulator spring 246, thereby storing the energy ofmaster cylinder actuation in the form of potential energy in the spring246. System pressure rises at a much slower rate during this phase ofpedal actuation, as represented by the shallow portion 288 of the curve282. This effect results from the fact that the incremental increase ininput force required to compress the spring 246 is substantially lowerthan the incremental increase in input force required to additionallypressurize the hydraulic fluid. As a result, resistance to brake pedalmovement during this second phase of brake pedal actuation increases ata much slower rate than during the first phase.

[0084] In the illustrated embodiment, the transition point 286 betweenthe first and second phases of brake pedal actuation occurs atapproximately 800-850 psi of hydraulic pressure. Pressure thereafterrises gradually to about 900-950 psi when the brake pedal 80 is latchedin its locked position and the end of the second phase of its actuationstroke. The compression spring 246 is compressed about {fraction (1/2)}″at this time. At least 50%, and possibly at least 65% or more, of thetotal pedal stroke required to latch the brake pedal 80 in its lockedposition is consumed in the second phase of brake pedal actuation. As aresult, by the end of this phase, more than ample energy is stored inthe accumulator 62 to hold the brakes 52 and to return the brake pedal80 with little additional effort by the operator. (The amount of energystored by the accumulator 62 is represented by the hatched area 292under the curve 282 in FIG. 9.)

[0085] Considerable work is performed over the rather lengthy secondphase of the brake pedal actuation stroke, but at much lower inputforces than would be required to perform the same amount of work (andhence to store the same amount of energy) over a shorter stroke. Infact, the transition point 286 is reached at an operator input force ofabout 35 lbs, and only an additional 25 lbs of input force is requiredto depress the brake pedal 80 to its latch point. This is in contrast tothe drastically higher input force that would be required to pressurizethe fluid to a much higher level if the operator were to press the brakepedal 80 to its latch point without an accumulator in the system (seethe phantom line 290 in FIG. 9). Hence, the accumulator 62 greatlyfacilitates brake pedal latching and reduces the precision required toachieve the latch point because the operator strokes the pedal a greatdistance easily.

[0086] Upon brake pedal release, the one-way restrictor valve 216immediately seats against the front end of the chamber 210 under theforce of the return spring 230, thereby preventing rapiddepressurization of the accumulator chamber 210. The damping effectprovided by this restricted fluid flow imposes a relatively low returnspeed on the brake pedal 80 that continues for a period of time. Thebrake pedal 80 consequently returns to its initial position without anyundesirable rapid snapback that otherwise would produce substantial wearand tear on the system and even risk injury to the operator. The dampinggrease between the brake pedal pivot shaft 86 and the stationary sleeve92 additionally damps brake pedal return movement at this time. However,the combined damping effect provided by the one-way restrictor valve 216and the damping grease does not overly-damp brake pedal return. Instead,the brake pedal 80 is biased by the springs 96 and 246 to quickly followthe operator's foot without pushing the foot upwardly too fast. Theremaining, small snapback impact forces resulting from this moderatereturn speed are absorbed by the elastomeric bumper 148 on the swing arm112 when the brake pedal 80 reaches its at-rest or fully releasedposition, resulting in a virtually noiseless and vibration less pedalreturn.

[0087]FIG. 10 depicts a hydraulic brake system 310 arranged similarly tohydraulic brake system 50 of FIGS. 1-3. Hydraulic brake system 310utilizes a drum brake system rather than a disk brake system to applybraking force at the wheels. Components of hydraulic system 310 whichare similar to the components described with respect to FIGS. 1-3 willbe referred to using identical reference numerals.

[0088] Of particular interest in FIG. 10, brake system 310 is embodiedas a drum brake system which includes a brake cylinder and shoe assembly312 which operates in response to hydraulic fluid pressure appliedthrough hydraulic control line 46. Brake cylinder and shoe assembly 312includes a brake cylinder which presses brake shoes radially outwardagainst brake drum 314. Brake drum 314 on its outboard side connects towheels 14. Application of hydraulic fluid pressure through hydrauliccontrol lines 46 causes brake cylinder and shoe assembly 312 to pressagainst brake drum 314, thereby generating a frictional force retardingmovement of wheels 14. Accordingly, hydraulic brake system 310 operatesas described above, except that application of braking pressure occursthrough a drum brake system rather than through a disk brake system.

[0089] In yet another embodiment of the present invention, FIG. 11depicts a hydraulic brake system 320 which utilized a band brake systemto retard movement of drive shafts 34. FIG. 11 is generally arranged asdescribed above with respect to FIGS. 1-3 and 10 except that the brakemechanism will be described with respect to a band brake system, ratherthan a disk or drum brake system. Accordingly, like reference numeralsfrom these figures will be used to described similar components in FIG.11.

[0090] Hydraulic brake system 320 utilizes displacement of brake pedal80 and linkage 42 to generate a hydraulic fluid pressure from mastercylinder 60 into hydraulic control lines 46. Hydraulic control lines 46operate a band brake assembly 322. Band brake assembly 322 includes abrake cylinder 324 rigidly connected to drive shaft 34. Brake cylinder324 is encircled by brake band 326. In response to hydraulic to fluidpressure, brake band 326 circumferentially restricts around brakecylinder 324 to generate a frictional force. A frictional force retardsmovement of drive shafts 34 and correspondingly retards movement ofwheels 14 to thereby crate a braking force. When hydraulic fluidpressure in hydraulic control line 46 is reduced, brake band 326 reducesthe circumferential constriction thereby reducing the braking force.

[0091] FIGS. 12-17 show a preferred embodiment of caliper assembly 48and its interconnection to golf car 10. FIG. 12 shows a left brakeassembly 500L which is composed of the integral hub and rotor assembly502 which has a rotor portion 504 and a wheel hub portion 505. Brakeassembly 500L further has a caliper assembly 506 which is attached bytwo through bolts 508 to affixed flange 510 rigidly mounted to the rearaxle housing 511.

[0092] Caliper assembly 506 has a caliper outboard half subassembly 512and a caliper inboard half subassembly 514. Caliper inboard half 514 hasan input fluid port 516 for receiving fluid from the hydraulic brakeline 521 and a fluid output port 517 for providing fluid to the rightbrake system 500R (see FIG. 13). Caliper inboard half subassembly 514has a bleeder valve 518 for bleeding air from the brake lines 521 duringrepair or installation.

[0093]FIG. 13 shows a right brake assembly 500R, which is composed ofthe same components as those shown in the left brake assembly 500L ofFIG. 12, in mirror image form. Caliper assembly 506 holds a pair ofbrake pads 518 and 519 adjacent to rotor 504 of the integrated hub androtor assembly 502. Pads 518 and 519 move in response to hydraulic forcegenerated by fluid under pressure applied to input port 516R. Theintegrated hub and rotor assembly 502 is held onto drive shaft 536 by ahex castle nut 538 and cotter pin 540.

[0094]FIG. 14 shows an exploded view of caliper assembly 506, whichreveals that the caliper inboard half subassembly 514 and caliperoutboard half subassembly 512 each have a pair of piston actuators 520.Each actuator has a conventional polymeric outside seal 522, whichelastically deforms when the pistons are moved forwardly to pressagainst the brake pads 518 and 519, and which undeform to pull thepiston away from the rotor portion 504 when the fluid pressure isremoved. Between the halves of the caliper 506 is a pair of conventionalelastomeric O-rings 525 which function to help prevent leakage ofhydraulic fluid moving through internal passages within each half subassembly 512 and 514 and between the halves of the caliper 506. Disposedimmediately adjacent the O-rings 225 is a pair of through holes 528 foraccepting through mounting bolts 530 (not shown) (in FIG. 14). Alsoshown is through bolt 532 which functions to secure brake pads 519 and518 in their proper alignment with the rotor portion 504. Wire springclips 542 and 544 generally are further provided to hold the brake padsin place.

[0095]FIG. 15 is a perspective view of caliper assembly 506 of thecurrent invention. Shown are the through bolts 530 which function tohold the caliper inboard half subassembly 514 and caliper outboard halfsubassembly 516 together. Also shown are through bolts 532 holding thebrake pads 518 and 519 in proper position between the piston actuators520.

[0096]FIG. 16 shows a bottom view of the caliper brake assembly 500.Shown is the relationship of the pads 518 and 519 with the actuatingpistons 520. As can be seen, the pads 518 and 519 define a space whereinthe rotor portion 504 is located.

[0097]FIG. 17 is a diagram of the integral wheel hub and rotor assemblywith caliper disposed within the small diameter of the golf cart wheel542. As can be seen, the low profile caliper 506 can fit within thesmall diameter of the golf cart wheel. The lower profile of the caliper506 allows for incorporation of a disk brake system onto a golf cart.

[0098] Further details of the brake caliper assembly 506 will now bedescribed. Subassembly 512 includes a metal caliper housing preferablyprepared from an iron or aluminum alloy casting, and subassembly 514includes a similarly made metal caliper housing. Each of these caliperhousings may be precision-machined to conventional tolerances to havetheir flat exterior mating surfaces, the through holes, andsubstantially cylindrical pockets for receiving the brake pistons, thatare shown in the FIGS. 12 through 15, formed to proper size. Usingconventional techniques, internal passages for hydraulic fluid areformed within caliper housings to provide hydraulic fluid from the inletport to the backside of the respective brake piston pockets. Flatmachined surfaces on the end portions of one caliper housing ofsubassembly 512 match up with and bear tightly against correspondingflat machined surfaces on the caliper housing of subassembly 514 whenthe two mounting bolts 530 are drawn tightly against the rigid mountingflange 510 to which the overall assembly 506 is rigidly mounted. Theside face of mounting flange 510 contacting the adjacent caliper housingof assembly 512 is parallel to the rotor 504. The through holes in thecaliper housings for the mounting bolts 530 are perpendicular to thesemachined surfaces, thus ensuring that faces of the brake caliper pistonsare sufficiently parallel to the parallel opposed faces of rotor 504 toensure substantially uniform wear on brake pads 518 and 519.

[0099] Each through bolt is substantially centrally positioned relativeto opposed flat machined surfaces of the end portions of the caliperhousings of caliper subassemblies 512 and 514. In this manner,tightening bolts 530 ensures slight compression of O-rings 525, toeliminate the possibility of any hydraulic leak between the adjacenthousings. Since only two bolts are required to mount caliper theassembly 512 to flange 510, minimal effort is required for finalassembly to the vehicle axle. This means that brake caliper assembly 512can be fully assembled in a location remote from the final assemblyplant for the small utility vehicle, function-tested, and then shippedwhile filled with hydraulic fluid if desired.

[0100] Caliper assembly 506 has a low compact profile when viewed inside elevation. As best shown in FIG. 17, the clearance between theradially outermost points of caliper housings of subassemblies 512 and514, and the inner generally cylindrical rim surface of the wheel arepreferably in the range of about 3 mm (about 0.1 inch) to about 20 mm(about {fraction (8/10)} inch), with a range of about 5 mm (about{fraction (2/10)} inch) to about 12 mm (about 2 inch) being presentlypreferred. Such tight clearances are made possible in part by usingsufficiently thick and stiff caliper housings which are furtherrigidified and stabilized by the use of two quality mounting bolts 530and a sufficiently stiff mounting flange to avoid any significantlateral or radial flexing or distortion of the caliper assembly duringintense braking, up to and including full rotor/wheel lock-up. In thisregard, the outer end portions of caliper housings through which thethrough bolts 530 are run, are as shown generally thicker (that is, inthe direction of the axis of the rear axle of the vehicle) than they arehigh (that is, a the radially outward direction from the axis of therear axle of the vehicle).

[0101] The use of two sets of opposing pistons in the opposed halfcaliper subassemblies 512 and 514 also provides additional benefits.First, the opposed piston arrangement provides balanced opposing forceson opposite sides of the rotor, thus allowing high hydraulic brakingforces to be applied. Secondly, the two piston actuators 520 insubassembly 512 are slightly angularly spaced apart from one another. Byusing two spaced-apart brake pistons on each caliper subassembly, agenerally oblong, kidney-shaped relatively thick brake pad may be usedas shown, thus maximizing the amount of surface area of the brake pad.Its large size helps minimize the rate of brake pad surface wear duringrepetitive braking over a period of months and years. The oblong brakepads are preferably made in any conventional or suitable manner, withreinforcing a back plate portion as shown, to help ensure minimaldeflection and good contact between the rotor surface and brake padsurface, even in the central region of the brake pad between the twobrake pistons. Armed with the teachings and illustrations within thepresent disclosure, the design and construction of compact, low-profiledual piston brake caliper assembly of the present invention with itslong-life brake pads need not be further described, since the design andconstruction of larger, less space-efficient conventional two-piston andfour-piston brake caliper assemblies are well understood, and detailsfrom those design and construction techniques, where space and compactis not an issue, can be readily adapted into the present environment.

[0102] While the invention has been described in its presently preferredform, it is to be understood that there are numerous applications andimplementations for the present invention. Accordingly, the invention iscapable of modification and changes without departing from the spirit ofthe invention as set forth in the appended claims.

1. A brake actuator assembly for a park and hold hydraulic brake systemof a vehicle comprising: (A) a brake pedal, for a hydraulic brakingsystem, which is pivotal, under the imposition of manual operatingforces, from an at-rest position 1) through an operating stroke in whichthe vehicle's brakes are engaged and in which said brake pedal returnsautomatically to said at-rest position upon release of the manualoperating forces to release the brakes, 2) through a locked positionwhich is located beyond an end of said operating stroke, and 3) to abeyond-lock position which is located beyond said locked position; (B) abrake pedal locking mechanism which cooperates with said brake pedal soas to 1) automatically latch said brake pedal in said locked positionupon movement of said brake pedal into said locked position, therebyholding the brakes in their engaged condition upon release of theactuating forces, and 2) automatically unlatch said brake pedal fromsaid locked position upon movement of said brake pedal into saidbeyond-lock position, thereby permitting return of said brake pedal tosaid at-rest position upon release of the actuating forces and releasingthe brakes; (C) an accelerator pedal; and (D) a kickoff mechanism whichcouples said accelerator pedal to said brake pedal locking mechanism andwhich actuates said brake pedal locking mechanism to unlatch said brakepedal from said locked position upon actuation of said acceleratorpedal.
 2. An actuator assembly as recited in claim 1 , wherein saidlocking mechanism has a single latch point which provides for a singlelocked position of said brake pedal and a single audible indication toan operator that said brake pedal has been depressed sufficiently to belatched in its locked position.
 3. A method of applying and holding ahydraulic brake of a vehicle comprising: (A) manually driving a brakepedal of a hydraulic braking system from an atrest position and into anoperating position; then (B) manually driving said brake pedal throughsaid operating position and to a locked position in which a lockingmechanism latches said brake pedal in said locked position, said lockedposition defining the sole position in which said brake pedal can belocked with the brakes engaged, said locking mechanism being latched insaid locked position, the locking mechanism providing a single audibleindication that said brake pedal has been depressed sufficiently to belatched in said locked position; then (C) unlatching said brake pedalfrom said locked position by one of 1) manually driving said brake pedalto a beyond-lock position which is located beyond said locked positionand in which said locking mechanism automatically unlatches said brakepedal, and 2) manually driving an accelerator pedal into engagement andautomatically displacing said locking mechanism to unlatch said brakepedal; and then (D) permitting said brake pedal to return to saidat-rest position.
 4. A method of applying and holding a hydraulic brakeof a vehicle comprising: (A) manually driving a brake pedal for ahydraulic brake system from an atrest position an operating position;then (B) manually driving said brake pedal through said operatingposition to a locked position in which a locking mechanism latches saidbrake pedal in said locked position; then (C) releasing said brake pedalwhile said brake pedal remains in its locked position; then (D)unlatching said brake pedal from said locked position by manuallydriving an accelerator pedal into a position in which said acceleratorpedal interacts with said locking mechanism to unlatch said brake pedaland to permit said brake pedal to return to said at-rest position. 5.The method according to claim 4 wherein during the step (B), saidlocking mechanism provides a single audible indication to an operatorthat said brake pedal has been depressed sufficiently to be latched insaid locked position.
 6. A method of energizing a hydraulically actuatedservice brake of a vehicle and holding said brake in its engagedcondition, comprising: (A) driving a brake pedal through an actuationstroke to manually actuate a master cylinder to generate hydraulicpressure, wherein, during a first phase of said actuation stroke, atleast substantially all work performed by said master cylinder isapplied toward hydraulic pressure intensification, and wherein, during asecond phase of said actuation stroke, at least a portion of the workperformed by said master cylinder is applied towards energy storage in ahydraulic accumulator; and (B) latching said brake pedal in a lockedposition in said second phase of said actuation stroke to hold saidservice brake in its engaged condition with the assistance of storedenergy from said accumulator, said step of latching including making asingle audible sound to indicate that the brake pedal is in said lockedposition.
 7. A brake actuator assembly for a park and hold hydraulicbrake system of a vehicle comprising: a brake pedal for a hydraulicbrake system, the brake pedal operable through an operating stroke to alock position, and a hydraulic brake pedal locking mechanism whichcooperates with said brake pedal to automatically latch said brake pedalin said locked position upon movement of said brake pedal into saidlocked position, thereby holding the brakes in an engaged position uponrelease of the actuating force, said movement of said brake pedal intosaid locked position includes a single audible indication to theoperator that said brake pedal has been depressed sufficiently to belatched in said locked position.
 8. The actuator assembly of claim 8further comprising an accelerator pedal.
 9. The actuator assembly ofclaim 9 further comprising a kickoff mechanism which couples saidaccelerator pedal to said brake pedal locking mechanism and whichactuates said brake pedal locking mechanism to unlatch said brake pedalfrom said locked position upon actuation of said accelerator pedal. 10.A method to control hydraulic brake actuation of a vehicle comprising:(A) manually driving a brake pedal to pivot from an at-rest position andinto an operating position; then (B) manually driving said brake pedalthrough said operating position and to a locked position in which alocking mechanism latches said brake pedal in said locked position,whereby said locking mechanism provides a single audible indication toan operator that said brake pedal had been depressed sufficiently to belatched in said locked position; (C) unlatching said brake pedal fromsaid locked position by selectively and alternatively 1) manuallydriving said brake pedal to an over-travel position which is locatedbeyond said locked position and in which said locking mechanismautomatically unlatches said brake pedal, and 2) manually driving anaccelerator pedal into engagement with a kickoff mechanism toautomatically manipulate said locking mechanism to unlatch said brakepedal; and then (D) permitting said brake pedal to return to saidat-rest position.